<p>Custom modules and add their own dates to the list the <a href="&topic:date_api/date-filter&">Date API Views filter</a> and <a href="&topic:date_api/date-argument&">Date API Views argument</a> can handle. See the following example for the way that core dates have been added:</p>
<pre>
/**
 * Implementation of hook_date_api_fields().
 * on behalf of core fields.
 * 
 * All modules that create custom fields that use the 
 * 'views_handler_field_date' handler can provide
 * additional information here about the type of
 * date they create so the date can be used by
 * the Date API views date argument and date filter.
 */
function date_api_date_api_fields($field) {
  $values = array(
    // The type of date: DATE_UNIX, DATE_ISO, DATE_DATETIME.
    'sql_type' => DATE_UNIX, 
    // Timezone handling options: 'none', 'site', 'date', 'utc'.
    'tz_handling' => 'site',
    // Needed only for dates that use 'date' tz_handling.
    'timezone_field' => '', 
    // Needed only for dates that use 'date' tz_handling.
    'offset_field' => '', 
    // Array of "table.field" values for related fields that should be 
    // loaded automatically in the Views SQL.
    'related_fields' => array(),
    // Granularity of this date field's db data. 
    'granularity' => array('year', 'month', 'day', 'hour', 'minute', 'second'),
  );

  switch ($field) {
    case 'users.created':
    case 'users.access':
    case 'users.login':
    case 'node.created':
    case 'node.changed':
    case 'node_revisions.timestamp':
    case 'files.timestamp':
    case 'node_counter.timestamp':
    case 'accesslog.timestamp':
    case 'comments.timestamp':
    case 'node_comment_statistics.last_comment_timestamp':  
      return $values;
  }
}
</pre>